There may not be a more significant biological threat than the malevolent release of B. anthracis spores, the causative agent of anthrax disease, over a major metropolis. With the inhalational form approaching 90% mortality, and a spore that can remain infectious for years, protection against this deadly disease is critical. The U.S. anthrax vaccine induces toxin-neutralizing protection in animal models. However, its composition is unknown, its immunogenicity is short-lived, and it does not protect against some strains of B. anthracis. Our preliminary data suggests bacillus near-iron transporter (NEAT) proteins, which function to acquire and import host heme during infection, can protect mice against anthrax disease following vaccination. In this application, we use our molecular understanding of NEAT protein function to create and test a novel vaccine composed of heme transporters. We hypothesize vaccination with bacillus NEAT proteins will induce neutralizing or opsonin-mediated responses to B. anthracis and protect vertebrate hosts from full-blown anthrax after infection with the most highly-virulent strains. Aim 1: Determine the mechanism of protection following vaccination with NEAT proteins. Recombinant NEAT domains will be evaluated for efficacy using a murine model of anthrax. Protective antibodies will be evaluated for activity using heme acquisition and opsonin-mediated assays. Aim 2: Determine if vaccination with NEAT proteins protects against fully-virulent B. anthracis. NEAT proteins will be evaluated for their ability to protect against fully-virulent B. anthracis using a well-accepted guinea pig model of anthrax under high-containment. Safe antigens will also be constructed by mutagenesis of key residues that mediate NEAT functionality. Since NEAT proteins are conserved in every major genus of Gram-positive pathogenic bacteria, this work also has universal appeal for vaccine development against related species.